Position detecting method, position detecting apparatus, exposure method, exposure apparatus, making method thereof, and device and device manufacturing method

ABSTRACT

In order to find the positional relation between the reference coordinate system XY which defines the movement of a substrate W and the arrangement coordinate system αβ which corresponds to a plurality of divided areas on the substrate W divided by street lines Sα and Sβ, the substrate W and an observation field are moved relatively. By allowing position detecting method marks Mk on the substrate W to visit the observation field, the street lines Sα and Sβ are detected in the observation field during the observation field. According to the results of the detection, an approximate arrangement coordinate system is corrected. The positional relation between the reference coordinate system XY and the arrangement coordinate system αβ is caught with high accuracy enough to allow the observation field to visit the position detection mark (Mk). Thus, by obtaining the arrangement coordinate system of the divided area in high speed with high accuracy, the highly precise exposure might be performed with improved throughput.

TECHNICAL FIELD

The present invention relates to a position detecting method, positiondetecting apparatus, an exposure method, exposure apparatus, and amaking method thereof, as well as a device and device manufacturingmethod. More particularly, the present invention relates to a positiondetecting method to detect a position of a plural divided areas whichare formed on a substrate; an apparatus on which the position detectingmethod in applied; an exposure used when semiconductor devices aremanufactured in lithographic process, in the method, exposure isconducted found on the result obtained by using the position detectingmethod; an exposure apparatus on which the exposure method is applied,and a making method thereof; as well as a device which is manufacturedby using the exposure apparatus and a manufacturing method thereof.

BACKGROUND ART

Conventionally, in a lithographic process for manufacturing asemiconductor device, liquid crystal display device and so forth, anexposure apparatus has been used. In such an exposure apparatus,patterns formed on a mask or reticle (to be genetically referred to as a“reticle” hereinafter) are transferred through a projection opticalsystem onto a substrate such as a wafer or glass plate (to be referredto as a “substrate or wafer” herein after, as needed) coated with aresist or the like.

In general, the semiconductor device is manufactured by using theexposure apparatus, and it is composed of a plurality of circuit patternlayers on a wafer. Therefore, the positioning of the shot area on thewafer and the reticle (to be referred to as “alignment” hereinafter)must be precisely performed when they are overlaid in the exposureapparatus. In order to position them in the apparatus precisely, theposition of the wafer must be detected correctly, and the techniques,for example, disclosed in the publication of Japanese unexamined patentapplication (refer to as “Japan laid-open”, hereinafter) No. H9-92591,have been proposed.

In such conventional position detecting methods, enhanced globalalignment (to be referred to as “EGA” hereinafter) is widely employed.In EGA, fine alignment marks, which are positioning marks transferredtogether with circuit patterns on the wafer, are measured at a pluralityof positions within the wafer, in order to precisely detect positionalrelations of the reference coordinate system and the arrangementcoordinate system (to be referred to as “wafer coordinate system”hereinafter). Wherein, the reference coordinate system defines themovement of the wafer, and the arrangement coordinate system defines thearrangement of the respective shot areas on the wafer. The arrangementcoordinate of the respective shot areas are then obtained by theleast-squares approximation or the like, and stepping is performed byusing the calculated result in accordance with the accuracy of the waferstage on exposure. EGA is disclosed in, for example, Japan laid-open No.S61-44429 and its corresponding U.S. Pat. No. 4,780,617. In order to usesuch EGA, the fine alignment mark formed on the predetermined positionon the wafer is observed by high magnifying power. However, theobservation field is essentially narrow under the observation with highmagnifying power. Therefore, prior to perform fine alignment, thefollowing detection for the reference coordinate system and thearrangement coordinate system is preformed to catch fine alignment markscertainly within the narrow observation field.

At first, the outer edge of the wafer, an object in the positioningdetection, is observed. The positional relation between the referencecoordinate system and the arrangement coordinate system are detected inthe predetermined accuracy derived from the position of the notch in theouter edge, the position of the orientation flat or the outer edge ofthe wafer. This detection procedure is referred to as “rough alignment”.

Then, the observation apparatus is moved to the wafer or vice versa,that is, relative movement of the observation apparatus and the waferaccording to the positional relations of the first approximationarrangement coordinate system obtained by rough alignment and thereference coordinate system. A plurality of search alignment marks iscaught within the relatively wider observation field, and the searchalignment marks are observed. Based on the search alignment marksobserved as mentioned above, the positional relation between thereference coordinate system and the arrangement coordinate system isdetected in higher accuracy than that obtained in the rough alignment.Such detection procedure is referred to as “search alignment”hereinafter. The observation field of the observation unit is set in anenough range to catch the search alignment mark when the inaccuracy isincluded in the positional relation between the reference coordinatesystem and the arrangement coordinate system detected in the roughalignment. Further, the accuracy for the detection of the positionalrelation between the reference coordinate system and the arrangementcoordinate system is set in an enough range for the fine alignmentperformed in next.

As mentioned above, the rough alignment and the search alignment aresequentially performed. Then, the wafer is moved against the observationunit or vise versa, according to the positional relation between thereference coordinate system and the second-approximated arrangementcoordinate system, which is obtained in the search alignment. Afterthat, a plurality of fine alignment marks on the wafer is caught in anarrow observation field to perform fine alignment.

In conventional position detecting methods, three alignments such asrough alignment, search alignment and fine alignment are sequentiallyconducted. Among them, both in the search alignment and rough alignment,the positions of a plurality of marks to be observed must be detectedafter they are caught in the observation field, wherein the wafer ismoved to the observation unit or vise versa. Therefore, it takes muchtime to detect the positions of the shot areas by using the conventionalmethod.

On the other hand, in the exposure apparatus, high through put is neededbecause this apparatus is employed for mass production of semiconductordevices. Therefore, the alignment procedure composed of three steps asmentioned above becomes a problem on the way to accomplish the highthrough put. Accordingly, it is expected that the new technology toshorten the alignment time, maintaining the present accuracy of thealignment.

The present invention has been made in consideration of theabove-mentioned situation. The first object of the present invention isto provide the position detecting method and a position detectingapparatus to conduct the position detection with high accuracy in ashort time.

The second object of the present invention is to provide the exposuremethod and the exposure apparatus with high accuracy and high throughput depending on the rapid and precise position detection.

The third object of the present invention is to provide the device onwhich fine patterns are precisely formed.

DISCLOSURE OF INVENTION

In the first aspect of the present invention, the present invention is aposition detecting method for detecting a position of a plurality ofdivided area formed on the substrate, comprising: moving a substrate toan observation field relatively; detecting a positional relation betweena reference coordinate system which defines said movement of a substrateand an arrangement coordinate system corresponding to said plurality ofa divided area while the relative movement is performing.

According to the position detecting method, the equal position detectionperformed in the search alignment may be conducted during the periodnecessary for fine alignment, in which the substrate and the observationfield are relatively moved. Conventionally, this period has been notused for the measurement for alignment. Therefore, the conventionalsearch alignment step may be skipped, and the positional relationbetween the reference coordinate system and the arrangement coordinatesystem is detected rapidly.

In the first position detecting method of the present invention, thedivided area on the substrate is divided by street lines, and thepositional relation is detected based on a detection result of thestreet line while the relative movement is performing. In this case, thestreet line is detected within the observation field, moving thesubstrate and the observation field relatively, when the two coordinatessystems are detected. One of the coordinate system is the referencecoordinate system for defining the movement of the substrate and theother is the arrangement coordinate system corresponding to thearrangement of a plurality of the divided areas divided by the streetlines on the substrate. The street line formed on the substrate issubstantially parallel to the coordinate axis of the arrangementcoordinate system. That is, the relation between the relative movementdirection of the substrate to the observation field and the directionalong the axis of the arrangement coordinate may be obtained bydetecting the street line in the observation field. The relativemovement direction is decided in the reference coordinate system.Furthermore, the street line is detected in the observation field,moving the substrate to the observation field or vice versa, i.e.,relative movement. As a result, the relation between the direction ofthe street line is formed and that of the relative movement is detectedaccurately, because the detection is not performed based on the streetline having short length caught at the moment in the observation field,but that having enough length caught there. Accordingly, the positionalrelation between the reference coordinate system and the arrangementcoordinate system may be detected in high speed, holding its accuracy.

The street lines divide an area to form divided areas on the substrate.In its extension direction, there are usually two directions beingperpendicular each other to divide the divided area into matrices.Accordingly, when the direction of the substrate is not decided prior tothe detection of the street line, even though one street line isdetected, it is not determine that the street line is extended whichdirection described above for the arrangement of the divided area.

Considering these, in the first position detecting method of the presentinvention, prior to the detection of the street line, an outer edge ofthe substrate is measured to obtain a result, and a positional relationbetween the reference coordinate system and the arrangement coordinatesystem is detected by using the result with a predetermined accuracy,which is lower than that detected while the substrate is moving to anobservation field relatively.

In this case, the outer edge of the substrate is measured to determineuniquely the relation between the arrangement direction of the dividedarea and the extension direction of the street line, which is caught inthe observation field, by using the result. For example, when thedivided areas are arranged in matrices and the extension directions oftwo street lines are perpendicular each other, the rotation direction isobtained less than 45° found on the measurement of the outer edge of thesubstrate. Accordingly, when one street line is detected, it isrecognized that the street line is extended to which array direction inthe divided area on the substrate.

When the positional detection is detected with the predeterminedaccuracy, the substrate may be rotated so that a direction along an axisof the reference coordinate system is substantially parallel with thedirection along an axis of the arrangement coordinate system based onthe positional relation detected with the predetermined accuracy. Thisrotation is performed according to the positional relation detected withthe predetermined accuracy based on the measurement result of the outershape of the substrate. In this case, in performing the relativemovement of the substrate and the observation field in below, since therelative movement direction may be set as the one of the axis directionof the reference coordinate system, the relative movement is controlledeasily.

Further, in the first position detecting method of the presentinvention, the observation field is moving to the substrate relativelyalong the street line. In this case, since the particular street line iscontinuously detecting, the accuracy in the position detection betweenthe reference coordinate system and the arrangement coordinate systemderived from the detection of the street line may be improved.

In the detection of the street line, a positional change of a borderbetween the divided area and the street line is measured by observing ofa moving picture in the range of the observation field to obtain aresult, while the relative movement is performed, and the positionalrelation is detected based on a measurement result of the change of theborder. In this case, the positional change between the border of thedivided area and the street line is measured by observing the movingpicture in the observation field while the substrate and the observationfield are moving relatively. Accordingly, the positional relationbetween the reference coordinate system and the arrangement coordinatesystem is detected in high accuracy and high speed. At that time, therelative movement of the substrate and the observation field is notdiscontinued, and the image-pick up apparatus having high-speed shutter,of which speed is enough high compared to that of the relative movement,is not needed, conducting the image pick-up in the observation field.

When it is presumed that the border is out of the range of theobservation field, the relative movement of the substrate to theobservation field may be corrected so that the border in the range ofthe observation field is continuously caught. According to the describedabove, since the border is continuously caught in the observation field,and it is assured to observe the border between the divided area and thestreet line extending over the enough length of the street line.Therefore, the relation between the direction of the street line isformed and that of the relative movement is detected reliably in highaccuracy.

Since the substrate and the observation field is relatively moved whenthe street line is detected, the images obtained as the image picked-upresult generally become blur images. When the object moves to the camera(i.e., the observation field) during pick-up time, if the time forpicking up image is not enough short against the velocity of therelative movement (i.e., the shutter speed is enough high). Then, theblur image is formed by the overlapped images caught at each moment.That is, the blur image is formed by the total amount of the light whichreached each points in the observation field during the predeterminedpick-up time. However, even though generating such blur image, themoving velocity of the border between the divided area and the streetline becomes enough slow in the observation field, when the observationfield is moved relatively along the street line. The moving direction ofthe border is perpendicular to that of the relative movement in theobservation field. On the contrary, in the area corresponding to thedivided area, the blur image having the brightness corresponding to meanreflectance of the divided area is formed. In the area corresponding tothe street line, the image having the brightness corresponding to meanreflectance of the street line is formed. In general, the meanreflectance in the divided area is different from that in the streetline.

In detection of the street line, an image formed by the total amount ofthe light which reached respective point in the range of the observationfield during predetermined time is picked-up; and the positional changeof the border in the range of the observation field is measured based onthe image pick-up result. In this case, the positional change of theborder between the divided area and the street line in the observationfield, i.e., the positional relation between the reference coordinatesystem and the arrangement coordinate system, may be detected by usingthe image pick-up result, the blur image, positively. For example, inthe above-mentioned case, the border between the divided area and thestreet line is detected by detecting the turning point of the brightnessin the obtained image. Then, the positional relation between thereference coordinate system and the arrangement coordinate system isdetected based on the detection result. Accordingly, the positionalrelation between the reference coordinate system and the arrangementcoordinate system is detected accurately, when the relative movementvelocity of the substrate and the observation field is fast. As aresult, the image pick-up apparatus of which image pick-up time isrelatively long and is commercially available may be used.

In the first position detection method of the present invention, therelative movement of the substrate to the observation field is performedto catch a predetermined number of position detection mark, which ischosen from a plurality of the position detection mark formed on thestreet line, in the observation field with predetermined order; theposition of the chosen position detection mark is detected; based on thedetection result, the positional relation may be detected with higheraccuracy than that detected during the relative movement.

With this, the street line is detected while the predetermined number ofthe position detection marks formed on the street line, i.e., finealignment marks, are moved in the observation field. Then, according tothe detection result, the positional relation between the referencecoordinate system and the arrangement coordinate system is detected inthe predetermined accuracy. The substrate and the observation fieldmoves relatively along the street line. The target position for movementof the position detection mark for the position detection mark to bevisited is corrected by using the detected positional detection, duringthis relative movement of the substrate and the observation field.Correcting the target position as mentioned above, based on thecorrected target position, the position detection marks are sequentiallydetected by moving the substrate and the observation field relatively.After detecting the predetermined number of the position detectionmarks, based on such position detection results, the positional relationbetween the reference coordinate system and the arrangement coordinatesystem are detected in high accuracy by using, for example, EGA method.Accordingly, in the present invention, since fine alignment is performedwithout conducting the conventional search alignment, the positionalrelation between the reference coordinate system and the arrangementcoordinate system are detected rapidly, keeping with its high accuracy.

In the second aspects of the present invention, the present invention isthe second position detecting method for detecting position of aplurality of divided areas which are divided by street lines on asubstrate by detecting a plurality of position detection mark formed onsaid street line, wherein the street line is detected when saidplurality of position detection mark is sequentially detected, and amoving route of said substrate is decided by using a detection result.

According to this, the street line is detected while the observationfield moves to a plurality of the position detection marks formed on thestreet line, i.e., fine alignment marks. According to the detectionresult, the positional relation between the reference coordinate systemand the arrangement coordinate system is detected in the predeterminedaccuracy. By using the detected positional relation, the target positionfor the position detection mark to be detected is corrected during thisrelative movement of the substrate and the observation field. Thuscorrecting the target position for movement, the position detectionmarks are sequentially detected based on the corrected target positionas mentioned above. Then, after detecting the predetermined number ofthe position detection marks, the positional relation between thereference coordinate system and the arrangement coordinate system isdetected based on the detection result in high accuracy by using, forexample, the EGA method. Accordingly, since fine alignment is performedwithout conducting the conventional search alignment, the positionalrelation between the reference coordinate system and the arrangementcoordinate system are detected rapidly, keeping with its high accuracy.

Also in the second position detecting method of the present invention,similarly to the first position detecting method, prior to the detectionof the street line, an outer edge of the substrate is measured and apositional relation between the reference coordinate system and thearrangement coordinate system may be detected by using the result. Inthis case, when one street line is detected, it is recognized that thestreet line is extended to which array direction of the divided area onthe substrate.

Furthermore, similarly to the case of the first position detectingmethod, by using the positional detection obtained from the measurementresult of the outer edge of the substrate, the substrate may be rotatedso that a direction along an axis of the reference coordinate system issubstantially parallel with the direction along an axis of thearrangement coordinate system. In this case, the same effects thatbrought by the first position detecting method of the present inventionis brought.

In the second position detecting method of the present invention,similarly to the first position detection method, the observation fieldmay be moved against the substrate relatively along the street line. Inthis case, similarly to the first position detection method, since theparticular street line is continuously detected, the accuracy of thedetection in the positional detection between the reference coordinatesystem and the arrangement coordinate system derived from the detectionof the street line may be improved.

In the detection of the street line, a positional change of the borderbetween the divided area and the street line in the observation fieldmay be measured by observing a moving picture in the range of the field,while moving the substrate to the observation field relatively. In thiscase, the positional change of the border between the divided area andthe street line in the field is measured by observing the moving picturein the field during the relative movement of the substrate and theobservation field. Accordingly, the positional relation between thereference coordinate system and the arrangement coordinate system may bedetected in high accuracy and high speed, when the image in theobservation field is picked up. At that time, the relative movement isnot discontinued, or the image pick-up apparatus having high-speedshutter, of which speed is enough high compared to that of the relativemovement is not used.

Furthermore, similarly to the first position detecting method, when itis presumed that the border is out of the observation field, therelative movement of the substrate and the observation field may becorrected so as to catch continuously the border in the range of theobservation field. In the detection of the street line, the image formedby the total amount of the light reached respective point in theobservation field during predetermined time is picked-up. Then, thepositional change of the border in the field may be measured by usingthe picked up image result. In this case, the same effect that broughtby the first position detecting method is brought.

In the third aspect of the present invention, the present invention is aposition detecting apparatus for detecting a plurality of divided areaon a substrate comprising: a position of a substrate stage which holdssaid substrate; a driving unit which drives said substrate stage; and anobservation system which observes said substrate while said substrate ismoved by said driving unit.

According to this, the substrate may be observed by the observationsystem while the substrate held by the substrate stage is moving.Therefore, the position detecting method is performed by the apparatusand the positional relation between the reference coordinate system andthe arrangement coordinate system may be detected in high speed.

In the position detecting apparatus of the present invention, thisapparatus may further comprise a control system for controlling thedriving unit to detect the street line, which divides the area on thesubstrate into the divided area, by using the observation system, movingsaid substrate stage, when the position detection marks on the substrateare detected. In this case, the control system moves the substrate stagethrough the driving unit so as to detect the street line in theobservation field, when the substrate is observed. Accordingly, thepositional relation between the reference coordinate system and thearrangement coordinate system may be detected accurately in high speed.

In the position detecting apparatus of the present invention, thecontrol system may be the structure wherein the driving unit iscontrolled by the control unit so as to trace the route to thepredetermined position detection mark which are chosen among theposition detection marks formed on the street line by the observationfield; the position of the predetermined position detection marks chosenare detected, and the position of the divided area is respectivelydetected by using the detection result of the predetermined detectionmark.

With this, the control system moves the substrate stage to sequentiallycatch the predetermined number of the position detection marks formed onthe street line, i.e., fine alignment marks, in the observation field ofthe observation system. During the movement of the substrate stage, theobservation system detects the street line. The control system detectsthe positional relation between the reference coordinate system and thearrangement coordinate system by using the detection result in thepredetermined accuracy, and the target position for movement for theposition detection mark to be detected is corrected, while the substratestage is moving. The control system thus corrects the target positionfor the movement, and the substrate stage is moved based on the targetposition for the movement, and then the position detection mark issequentially detected. The control system detects the positionalrelation between the reference coordinate system and the arrangementcoordinate system, according to detection result of the predeterminednumber of the position detection marks, by using, for example, EGAmethod, in high accuracy. According to the detection result, thepositional relation between the reference coordinate system and thearrangement coordinate system is detected in the predetermined accuracy.Accordingly, in the present invention, since fine alignment is performedwithout conducting the conventional search alignment, the positionalrelation between the reference coordinate system and the arrangementcoordinate system are detected rapidly, keeping with its high accuracy.The route may be along the street line.

The forth aspect of the present invention, the present invention is theexposing method wherein a predetermined pattern is transferred to adivided area on a substrate by emitting an energy beam comprising, priorto the transfer, detecting a position of said divided area formed on thesubstrate by using the position detecting method of the presentinvention. According to this, the position of the divided area formed onthe substrate may be accurately detected by using the position detectingmethod of the present invention in high speed; then, the predeterminedpatterns are transferred to the substrate by exposing second layer andsubsequent layers for the divided area. Accordingly, multilayer exposureis conducted to form multilayer patterns, holding the overlay accuracyin enhanced through put.

In the fifth aspect of the present invention, the present invention isthe exposure apparatus for transferring the predetermined pattern to thedivided area on the substrate by emitting energy beam comprising: anillumination system for emitting the energy beam; and the positiondetection apparatus of the present invention for detecting the positionof the divided area. With this, the predetermined pattern is transferredonto the divided area after high speed and high accuracy positiondetection is performed by detecting the position of the divided areaformed on the substrate with the position detecting apparatus of thepresent invention. Therefore, the multilayer exposure may be conductedto form multilayer patterns, holding the overlay accuracy among layersin enhanced through put.

In the sixth aspect of the present invention, the present invention isthe making method for an exposure apparatus wherein the predeterminedpattern is transferred to the predetermined divided area on a substrateby emitting energy beam comprising: providing the illumination systemfor emitting the energy beam; providing the substrate stage for holdingthe substrate; providing the driving unit for driving the substratestage; providing a observation system for observing the substrate duringmovement the substrate stage by the driving unit. According to this, theillumination system, position detecting apparatus, and other variousparts and devices are connected and assembled mechanically, opticallyand electrically, and adjusted, thereby the exposure apparatus fortransferring the pattern onto the substrate may be produced.

The making method for the exposure apparatus of the present inventionmay further comprise providing the control system for controlling thedriving unit to detect the street line, which divides the area on thesubstrate into the divided area, in the observation system, moving thesubstrate stage, when the mars on the substrates are detected. In thiscase, the apparatus as follows is made, wherein the control unit movesthe substrate stage in the observation field of the observation systemthrough the driving unit, observing the substrate by the observationsystem.

Furthermore, in the lithography step, the device having fine patterns onit may be manufactured by exposing the substrate with the exposureapparatus of the present invention to transfer the predetermined patternonto the substrate. Accordingly, the present invention is the deviceproduced by using the exposure apparatus of the present invention inanother view point, and also it is the manufacturing method of device byusing the exposure method of the present invention to transfer thepredetermined pattern onto the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing the schematic arrangement of an exposureapparatus according to one embodiment.

FIG. 2 is a view for explaining the rough alignment detection system ofthe apparatus in FIG. 1.

FIG. 3 is a perspective view for explaining the principle of scanningexposure performed by the apparatus in FIG. 1.

FIG. 4 is a flow chart of an alignment procedure prior to exposure forthe second layer and subsequent layers.

FIG. 5 is a view showing arrangements as an example of chip areas andstreet lines on the wafer.

FIG. 6 is a view showing as an example of sites of position detectionmarks formed.

FIGS. 7A to 7C are views for explaining the image in the observationfield.

FIG. 8 is a flow chart for explaining the device manufacturing method byusing the exposure apparatus shown in FIG. 1.

FIG. 9 is a flow chart showing the processing step in FIG. 8.

BEST MODE FOR CARRYING OUT THE INVENTION

An exposure method and exposure apparatus according to an embodiment ofthe present invention will be described below with reference to FIGS. 1to 9.

FIG. 1 shows the schematic arrangement of an exposure apparatus 100according to one embodiment of the present invention. The exposureapparatus 100 is a scanning type projection exposure apparatuscomprising a position detecting apparatus based on a so-calledstep-and-scan exposure method.

The exposure apparatus 100 comprises: the illumination system 10 foremitting illumination light for exposing the wafer, reticle stage RSTserving as a mask stage for holding the reticle R as a mask; aprojection optical system PL; the wafer stage WST for movingtwo-dimensionally the wafer W as the substrate within the X-Y plane; therough alignment detecting system RAS for observing outer edge of thewafer W; the alignment detecting system AS as the observing system forobserving fine alignment mark as position detecting marks or streetlines, and the control system for controlling thereof.

The illumination system 10 includes: the light unit; a shutter, thesecondary light source forming optical system, a beam splitter, acondenser lens system, a reticle blind, and an image lens system, whichare not shown in FIG. 1. The respective components of the illuminationsystem 10 are disclosed Japan laid-open No. H9-320956. As the lightsource unit, followings are used: KrF excimer laser beam (wavelength=248nm), ArF excimer laser beam (wavelength=193 nm), F₂ laser beam(wavelength=157 nm), Kr₂ (krypton dimer) laser beam (wavelength=146 nm),Ar₂ (argon dimer) laser beam (wavelength=126 nm), high harmonicgeneration devices such as copper vapor laser or YAG laser harmonics, anultra-high pressure mercury vapor lamp (e.g., g-line or i-line), or thelike. Alternatively, instead of the light, which is emitted from theabove-mentioned light source, beam such as charged electron x-ray andelectron beam might be used.

Function of the illumination system 10 composed as described above isbriefly explained. The light beam, which is emitted from the lightsource, reaches the secondary light source forming optical system whenthe shutter is opened, thereby many secondary light sources are formedat the emission terminal of the secondary light source optical system.The illumination light from the secondary light source that passesthrough both the beam splitter and the condenser lens system, and reachthe reticle blind. Then the illumination light passed through thereticle blind is emitted to the mirror M through the image lens system.

The mirror M bends the optical path of the illumination light beam ILvertically down load, and then the light beam illuminates theillumination area IAR portion (see FIG. 3) formed as the rectangularshape on the reticle R, which is held on the reticle stage RST.

The reticle R is fixed on the reticle stage RST, for example, by vacuumchucking. In order to position the reticle R, the reticle stage RST isstructured so that it can be finely driven two-dimensionally (in theX-axis direction, the Y-axis direction perpendicular to the X-axisdirection, and the rotational direction around the Z-axis perpendicularto the X-Y plane) within a plane perpendicular to an optical axis IX(coinciding with an optical axis AX of the projection optical system PL,which will be described later) of the illumination optical system.

The reticle stage RST can be moved on a reticle base (not shown inFIGS.) in a predetermined scanning direction (Y-axis direction in thiscase) at a designated scanning velocity by a reticle driving portion(not shown in FIGS.) structured of a linear motor or the like. It has amovement stroke which the entire surface of the reticle R can at leastcross the optional axis IX of the illumination optical system.

On the reticle stage RST, a moving mirror 15 for reflecting a laser beamfrom a reticle laser interferometer (to be referred to as a “reticleinterferometer” hereinafter) 16 is fixed. The reticle interferometer 16detects the position of the reticle stage RST within the stage movementplane at all times by for example, a resolution of about 0.5 to 1 nm. Inpractice, a moving mirror which has a reflecting surface perpendicularto the scanning direction (Y-axis direction) and a moving mirror whichhas a reflecting surface perpendicular to the non-scanning direction(X-axis direction) are mounted on the reticle stage RST. Also, thereticle interferometer 16 is arranged on one axis in the scanningdirection, and on two axes in the non-scanning direction. However, inFIG. 1, these are represented as the moving mirror 15 and reticleinterferometer 16.

Positional information of the reticle stage RST is sent from the reticleinterferometer 16 to a stage control system 19 and to the maincontroller 20 via the stage control system 19. The stage control system19 drives the reticle stage RST through a reticle driving portion (notshown in FIGS.) by instructions from the main controller 20 based on thepositional information of the reticle stage RST.

A reticular alignment system (not shown in FIGS.) determines the initialposition of the reticle stage RST so that the reticle R is accuratelypositioned at a predetermined reference position. Therefore, theposition of the reticle r can be measured with a sufficiently by onlymeasuring the position of the moving mirror 15 with the reticleinterferometer 16.

The projection optical system PL is arranged below the reticle stage RSTin FIG. 1. The direction of the optical axis AX (which coincides withthe optical axis IX of the illumination optical system) of theprojection optical system PL is the Z-axis direction. In order to makethe projection optical system PL double telecentric, a refractionoptical system configured of a plurality of lens elements arranged atpredetermined intervals along the optical axis AX is employed. Theprojection optical system PL is a reduction optical system having apredetermined projection magnification of, for example, ⅕, ¼ or ⅙.Therefore, when the illumination area IAR of the reticle R isilluminated with the illumination light IL from the illumination opticalsystem, a reduced image (partial inverted image) of the circuit patternof the reticle R in the illumination area IAR is formed on the wafer Wwhich surface is coated with a photo-resist.

The wafer stage WST can be in the Y-axis direction that is in thepredetermined scanning direction (Y-axis direction is shown as the rightor left direction in FIG. 1) or the X-axis direction that isperpendicular to the Y-axis direction (the X-axis direction is shown asthe perpendicular to the sheet of FIG. 1), for example, by a twodimensional linear actuator. The substrate table 18 is fixed on thewafer stage WST. The wafer holder 25 is mounted on the substrate table18. The wafer W as a substrate is held on the wafer holder 25 by vacuumchucking. The substrate stage is composed of the wafer stage WST, thesubstrate table 18, and the wafer holder 25.

The substrate table 18 is mounted on the wafer stage WST of whichposition is fixed in X-Y axis direction but allowing to move or tiltZ-axis direction. The substrate table 18 is supported by three shafts,which are not shown in the figures. These three shafts are independentlydriven by the wafer driving unit 21 in Z-axis direction to establish theface position of the wafer W held on the substrate table 18 (theposition in Z-axis direction and the tilt on X-Y plane) in predeterminedsituation. Furthermore, the wafer holder 25 can rotate along the Z-axis.Accordingly, the wafer holder 25 is driven in 6 degrees of freedom bythe two-dimensional linear actuator or the driving unit. However, thetwo dimensional linear actuator or the driving unit is shown in FIG. 1as the typical example.

On the substrate table 18, a moving mirror 27 is fixed for reflecting alaser beam from a wafer laser interferometer (to be referred to as a“wafer interferometer” hereinafter) 28. The wafer interferometer 28arranged externally detects the position of the wafer W in the X-Y planeat all times with a resolution of about 0.5 to 1 nm.

In the practice, a moving mirror which has a reflecting surfaceperpendicular to the Y-axis direction, that is the scanning direction,and a moving mirror which has a reflecting surface perpendicular to theX-axis direction, that is the non-scanning direction, are on thesubstrate table 18. The wafer interferometer 28 is arranged on one axisin the scanning direction, and on two axes in the non-scanningdirection. However, in FIG. 1, these are represented as the movingmirror 27 and wafer interferometer 28. The positional information (orvelocity information) is sent to the stage control of system 19 and tothe main controller 20 through the stage control system 19. The maincontroller 20 instructs the stage control system 19 to control and drivethe wafer stage WST via a wafer driving unit 21. A control system isstructured of main controller 20 and the stage control system 19.

Alternatively, on the substrate table 18, a reference mark plate asmentioned in below, which is not shown in FIGS., is fixed. The markplate, on which several kinds of the reference marks are formed, is usedto measure the distance from the detection center in the alignmentdetection system AS to optical axis in the projection optical system PL.

The rough alignment detection system RAS is held at the position distantfrom the projection optical system PL and upward of it by using theholding member, which is not shown in FIGS. The rough alignmentdetection system RAS is composed of three rough alignment sensors 40 a,40 b, and 40 c, all of which detect the position of three points on theouter edge of the wafer W. Wafer W is carried by the wafer loader, notshown in FIGS., and it is held on the wafer holder 25. These three roughalignment sensors 40 a, 40 b, and 40 c are placed at the positions oncircumference of a circle which has predetermined radius (this radius isthe almost same as that of the wafer) so that the central angle is setto 120 degrees. Among them, the rough alignment sensor 40 a is placed atthe position, wherein the sensor 40 a is capable of detecting a notch N(the notch is a V-shaped cutout) formed on the wafer W held on the waferholder 25. As the rough alignment sensor, an image processing methodsensor composed of an image pick-up device and image processing circuitis used.

Return to FIG. 1, the alignment system AS is arranged at the side of theprojection optical system PL. In this embodiment, an off-axis alignmentmicroscope is employed, in which the microscope is composed of animaging alignment sensor to observe the street lines or marks forposition detection (fine alignment marks) formed on the wafer. Thedetailed structure of this alignment system AS is disclosed in, forexample, Japan laid-open No. H9-219354, and its correspondent, U.S. Pat.No. 5,859,707. The disclosure described in the above is fullyincorporated by reference herein, as far as the law of the countriesdesignated in a request or elected in a demand for the application filedin the country of origin permits them. The image of the wafer W observedin the alignment system AS is transmitted to the main controller 20.

The apparatus in FIG. 1 further includes a multiple focal positiondetection system for detecting the positions of the range within theexposure area IA (to be referred as “the area on the wafer whichconjugates to above-mentioned illumination area IAR”: see FIG. 3) on thesurface of the wafer W and the area around it in the Z direction (thedirection of the optical axis AX). The multiple focal position detectionsystem is one of a focus detection system based on the oblique incidentlight method. The multiple focal position detection system, not shown inFIGS., is configured of an emitting optical system and a light-receivingoptical system. For example, the emitting optical system includes anoptical fiber bundle, condenser lens, pattern forming plate, lens,emitting object lens, and the like (none of which are shown). Thelight-receiving optical system includes a condenser object lens, arotational direction vibration plate, and image forming lens, alight-receiving slit plate, a light-receiving unit having manyphotosensors, and the like (none of which are shown). The detailedstructure of this multiple focal position detection system is disclosedin, for example, Japan laid-open No. H6-283403 and its correspondingU.S. Pat. No. 5,448,332. The disclosure described above is fullyincorporated by reference herein, as far as the law of the countriesdesignated in a request or elected in a demand for the application filedin the country of origin permits them.

The operation principal of the scanning exposure by using the exposureapparatus 100 will be briefly described. With the exposure apparatus 100of this embodiment, as shown in FIG. 3, the reticle R is illuminatedwith the rectangular (slit-shaped) illumination area IAR, of whichlongitudinal direction is perpendicular to the scanning direction ofreticle R (Y-axis direction). On exposure, the reticle R is scanned inthe −Y direction at a velocity V_(R). The illumination area IAR (whichcenter almost coincides with the optical axis AX) is projected on thewafer W through the projection optical system PL. As a consequence, aslit-shaped projection area conjugate to the illumination area IAR,i.e., the exposure area IA, is formed. Since the wafer W and reticle Rhave an inverted image forming relationship, the wafer W is scanned in adirection (+Y direction) opposite to the direction of the velocity V_(R)at a velocity V_(W) in synchronism with the reticle R. Thus, the entiresurface of a shot area SA on the wafer W can be exposed. The scanningvelocity ratio V_(W)/V_(R) accurately corresponds to the reductionmagnification of the projection optical system PL. The pattern on apattern area PA of the reticle R is accurately reduced and transferredonto the shot area SA on the wafer W. The semiconductor circuit patternis formed on the chip area CA as a divided area in the shot area SA. Thewidth of the illumination area IAR in the longitudinal direction is setto be larger than that of the pattern area PA on the reticle R, butsmaller than the maximum width of a light-blocking area ST. Therefore,by scanning the reticle R, the entire area of the pattern area PA isilluminated.

The operation of exposure by exposure apparatus 100 will be brieflydescribed.

First of all, in this embodiment, the first layer is exposed. Onexposing the first layer, the reticle R on which a pattern for the firstlayer is formed is loaded onto the reticle stage RST by a reticle loader(not shown in FIGS.). Similarly, the wafer W to be exposed is loadedonto the substrate table 18 by the wafer loader.

Subsequently, the rough alignment for the wafer W loaded onto thesubstrate table 18 is conducted. In this rough alignment procedure, themain controller 20 moves the substrate table 18 through the stagecontroller system 19 and stage driving unit 21 to roughly position thewafer. In this positioning, the notch N is located directly below therough alignment sensor 40 a, and edge of the wafer W is located alsodirectly below the rough alignment sensors 40 b and 40 c.

On this condition, the rough alignment sensor 40 a detects the positionof the notch N formed at the edge of the wafer W. The rough alignmentsensors 40 b and 40 c detect the position of the edge of the wafer W.These detection results obtained by the sensors are transmitted to themain controller 20. In order to adjust the direction of wafer W by usingthe detection results provided from the rough alignment sensor 40 a, 40b, and 40 c, the main controller 20 drives in rotation the wafer holder25 through the stage control system 19 and the wafer driving unit 21.

Then, exposure for the first layer is performed. In this exposureprocedure, first of all, the substrate table 18 is moved to so that theX-Y position of the wafer W becomes the starting position for scanningto expose the first shot area on the wafer W. The main controller 20moves the substrate table through the stage control system 20 and thewafer driving unit 21. Simultaneously, the reticle stage RST is moved sothat the X-Y position of the reticle R becomes the starting positionsfor scanning. The main controller 20 moves these stages through thestage control system 19, the reticle driving portion (not shown inFIGS.), or the like.

Responding to the instruction from the main controller, the stagecontrol system 19 then performs scanning exposure by moving the reticlestage R and the wafer W relatively through the reticle driving portion,not shown in FIGS., and the wafer driving unit 21. This scanningexposure is performs according to the Z-positional information of thewafer detected by the multiple focal position detecting system, X-Ypositional information of the reticle R measured by the reticleinterferometer 16, and the wafer positional information measured by thereticle interferometer 31, adjusting the surface position of the waferW. During scanning exposure, reticle R and the wafer W are relativelymoved.

When exposure on the first shot area is thus finished, the substratetable 18 is moved so as to set the starting position for scanning toexpose the next shot area. Simultaneously, the reticle stage RST is alsomoved so that the X-Y position of the reticle R becomes the startingposition for scanning. Then, the scanning exposure to the shot area isperformed in the same manner as that of the exposure on the first shotarea. The scanning exposure for each shot area is similarly performed,and exposure on the first layer is completed.

When exposure on the first layer is completed, the wafer W is removedfrom the exposure apparatus 100, and the wafer W is developed, andetched. Then, a new film is formed on the wafer W, and the film surfaceis polished, and photoresist is coated on the film surface. Afterperforming such processes, exposure on the second layer is performed. Inorder to form a circuit pattern which is accurately overlaid on thepattern previously formed, the positional relation between the thereference coordinate system (X, Y) and the arrangement coordinate system(α, β) is detected precisely, and then exposure is performed, by usingthe detection result, as mentioned below. The reference coordinatesystem (X, Y) defines the movement of the wafer W, i.e., the movement ofthe wafer stage WST. The arrangement coordinate system (α, β) relates tothe arrangements of the circuit pattern formed on the wafer W, i.e., thearrangements of the chip areas.

The detection of the positional relation between the referencecoordinate system (X, Y) and the arrangement coordinate system (α, β) inthe embodiment of the present invention will be described below withreference to FIGS. 4 to 7. FIG. 4 is a flowchart showing an example ofthe detection for the positional relation.

First of all, after the predetermined preparation procedure is finished,the reticle R on which the pattern should be formed on the second layeris loaded onto the reticle stage RST by using the reticle loader.Subsequently, the main controller 20 performs the reticle alignment andthe measurement of the base line by using the reticle microscope, thereference mark plate on the substrate table 18, and the alignment systemAS, which are not shown in FIGS.

After this procedure, in step 201 on FIG. 4, the wafer W is loaded onthe substrate table 18 by the wafer loader to expose the second layer.As shown in FIG. 5, on the wafer W, the chip area CA (i, j) (i=1 to m−1,j=1 to n) are formed, and they are divided into matrices by the streetlines. The street line Sα_(i) (i=1 to m−1) extends to the α directionand the street line Sβ_(j) (j=1 to n−1) extends to the β direction. InFIG. 5, signs are given to the chip areas placed in each corner, CA (1,1), CA (1, n), CA (m, 1), CA (m, n), except other chip area (i, j). Asshown in FIG. 5, the chip area CA (i, j) (i=2 to m−1, j=2 to n−1) aresurrounded by the street lines Sα_(i−1), Sα_(i), Sβ_(j−1), and Sβ_(j).Furthermore, as shown in FIG. 6, the position detection mark MX (i, j)is formed on the street line Sα_(i−1), which close to each chip area CA(i, j) XL0 distant from the left upper corner of the FIG. 6 in the αdirection, according to each chip area CA (i, j). The detection mark MY(i, j) is formed on the street line Sβ_(i−1) close to each chip area CA(i, j) YL0 distant from the left upper corner of the FIG. 6 in the −βdirection, according to each chip area CA (i, j).

Return to FIG. 4 again, the rough alignment is similarly conducted asdescribed above for the wafer W loaded in step 203. On this condition,the main controller 20 is transmitted the detection results from therough alignment sensors 40 a, 40 b, and 40 c, the first approximationarrangement coordinate system (α′, β′), which is coincide with thearrangement coordinate system (α, β) on the wafer W in the accuracywithin rough alignment, is calculated according to the results. The maincontroller 20 might rotationally drive the wafer holder 25 to coincidethe X- and Y-direction with α′- and β′-direction, respectively. In thiscase, the reference coordinate system (X, Y) coincides the firstapproximation arrangement coordinate system (α′, β′). The descriptionbelow is premising that the reference coordinate system (X, Y) coincidesthe first approximation arrangement coordinate system (α′, β′).

In step 205, then, according to the first approximation arrangementcoordinate system (α′, β′), the main controller 20 drives the wafer W bymoving the substrate table 18 so that the observation field of thealignment system AS include the border of the nearest street line to thenotch N and the chip area CA. In order to minimize the error between theposition obtained from the first approximation arrangement coordinatesystem (α′, β′) and the true position, the target position for movementis in the observation field which includes the border between thenearest street line to the notch N and the chip area CA. In the case ofthe arrangement as shown in FIG. 5, the nearest street line to the notchN becomes street line Sβ_(n/2) when n is an even number, andSβ_((n−1)/2) or Sβ_((n+1)/2) when n is an odd number. As shown in FIG.6, when the position detection mark MX (i, j) and MY (i, j) is formed,the border between the street line and chip area CA, which is the targetposition for the movement, is the border between the nearest street lineSβ₁₀ (one of the above-mentioned street line Sβ_(n/2), Sβ_((n−1)/2), andSβ_((n+1)/2)) and the chip area CA (1, J₀+1). This derives from thefollowing reasons: this border is closed to the notch N, and the wafer Wis moved along the street line in the direction of the upper left cornerin the chip area CA (i, j) to visit the detection position mark withinthe observation field as described below.

Return to FIG. 4, when the substrate is completed to move in step 205,the border between the street line Sβ_(j0) and the chip area CA (1,j₀+1) is searched within the observation field of the alignmentdetection system AS in step 207. When the border is not detected, theborder is searched, moving the wafer W around the position, and then theborder is caught within the observation field. The border at that timeand in below is detected by using the image processing in the maincontroller 20. Instead of the image processing in the main controller20, the specific image processing apparatus may be used. The position ofthe observation field at the timing is referred to as “the initialposition of the observation field”. The range of the observation fieldis represented as a thick solid square in FIG. 7A, and it is smallerthan those of the chip area CA or width of the street line Sβ_(i) orSβ_(j) to detect the position detection mark MX (i, j) or MY (i, j) withhigh accuracy. Accordingly, the image shown in FIG. 7B or 7C isobserved, when the chip area CA and the street line Sα and Sβ are in theobservation field.

Back to FIG. 4, the main controller 20 chooses p in number of theposition detection marks among the position detection marks MX (i, j)and MY (i, j) to decide the visiting order for the observation field.The position detection marks chosen are used to obtain the precisepositional relation between the reference coordinate system (X, Y) andthe arrangement coordinate system (α, β). In below, the chosen positiondetection marks p in number are represented by using suffix in thevisiting order, as the position detection mark M_(k) (k=1 to p). Themain controller 20 decides the moving route of the wafer W on which theobservation field of the alignment system AS traces from the initialposition of the observation field, when the AS sequentially visits theposition detection mark M_(k). The information for the moving route isreferred to as the “moving route information RT”. This moving routeinformation RT is composed of, for example, two information: one is theinformation for the street line order on which the observation fieldtraces when the field moves from the above described initial position orthe position of the position detection mark M_(k−1) to M_(k) (referredto as the “order information SQ_(k)”), and the other is the markinformation related to the position detection mark M_(k) to be detected(referred to as the “mark information MP_(k)”). The mark informationM_(k) is further composed of the chip area information andidentification information. The chip area information is correspondingto the position detection mark M_(k) (the arranged position of the chiparea CA (i, j), that is, (i, j); referred to as the “chip areainformation CID_(k)” hereinbelow). The identification information showswhether the mark detected is MX (i, j) or MY (i, j). Herein, the movingroute information RT is represented as follows: by arranging the orderinformation SQ_(k) and the mark information MP_(k) in sequential orderof timing they used.RT=(SQ₁, MP₁, SQ₂, MP₂, . . . , SQ_(p), MP_(p))MP_(k)=(CID_(k), MID) (k=1 to p)

Since the contents of the order information is the order of the streetline on which the observation field should trace when the field movesfrom the initial position or the position detection mark M_(k−1) to thatof M_(k), the designation of the contents are varied.

For example, the position detection mark MX (i, j) shown in FIG. 6 isset as the position detection mark M₁ to be visited firstly. Then, theobservation field might trace the street line β_(j0) from the initialposition of the field, i.e., the position of the field which catches theborder between the street line Sβ_(j0) and the chip area CA (1, j₀+1).Then, the field trace the street line Sβ_(j0) to reach the street lineSα_(i−1). After that, the field might reach the corner of the chip areaCA (i, j) (the left upper corner in FIG. 6 by tracing the street lineSα_(i−1). Furthermore, by designating (i, j) to the chip areainformation CID₁ as the contents of the mark information MP₁, themovement of the observation field may be stopped at the corner of thechip area CA (i, j) (as shown in the left upper corner of FIG. 6.Alternatively, by designating MX mark (i, j) to the identificationinformation MID₁, the observation field is moved onto the positiondetection mark MX (i, j) from the corner of the chip area CA (i, j).

Since the initial position of the observation field is known,designation of the street line Sα_(i−1) is enough as the orderinformation SQ₁ on which the field should trace from the initialposition to that of the position detection mark M₁ for first visiting.Therefore, as the contents of the order information SQ₁, for example,the street line Sα_(i−1) alone may be designated.

As the same manner that the order information SQ₁ is designated, thecontents of the order information SQ_(k) might be designated, when thefield visits to the position detection mark M_(k1) after visiting themar M_(k−1). The explanation will describe hereinbelow, premising theorder information SQ_(k) is set as described above.

The parameter k is set to 1 to show the position detection is conductedto detect the initial position detection mark M₁ in step 211.

Then, in step 213, the wafer W is moved to β′ direction (i.e.,Y-direction), which is presumed as β direction and is one of thearrangement direction of the chip area CA (i, j). At this time, theobservation field traces the street line Sβ_(j0) along −β direction. Theimage in the observation field of then is shown as those in FIGS. 7B and7C, and these images move up and down in the both FIGS. During themovement, the main controller 20 incorporates the image information inthe observation field through the alignment detection system AS atregular intervals, to detect the border position between the respectivechip areas CA (i, j₀+1) and the street line Sβ_(j0) in each time.

The reference coordinate system (X, Y) and the arrangement coordinatesystem (α, β) does not generally correspond each other. As shown in theFIGS. 7B and 7C, the angle between by X-axis and β-axis is θ. The movingvelocity of the wafer W (i.e., the moving velocity of the substratestage 18) is represented as V_(Y), the moving velocity of the border inthe observation field to X-direction V_(X) is represented as follows.V _(X) =V _(Y)×cot θOn the other hand, the reference coordinate system (X, Y) coincides withthe arrangement coordinate system (α, β) in the accuracy obtained in therough alignment. Therefore, θ may be not accurately 90°, but it showsthat the value almost 90°. As a result, when the velocity V_(Y) is toohigh to obtain the substantial static image, the movement of the bordermay be observed as the static image, because the moving velocity toX-direction of the border in the observation field, V_(X) becomes small.In the observation image, for example, as shown in FIG. 7B, the image ofthe chip area CA (i, j) is obtained as that having average brightness ofthe images in the chip area CA (i, j); the image of the street lineSβ_(j) is that having average brightness of the images in the streetline Sβ_(j). Accordingly, the turning points may be recognized as theborder.

As mentioned above, the main controller 20 detects the border positionbetween the chip area CA (i, j₀+1) and the street line Sβ_(j0) atregular intervals, as well as calculate the change of the borderposition in the observation field. Then, according to the change of theborder position obtained, the controller 20 detects the positionalrelation in the rotation direction between the reference coordinatesystem (X, Y) and the arrangement coordinate system (α, β), for example,the angle θ between the X-axis and β-axis. The main controller 20corrects the first approximation arrangement coordinate system (α′, β′)based on the detection results. In the detection, longer the distancefrom the street line Sβ_(j0) to the images in the observation field isused, higher the detection accuracy. Therefore, it is preferable thatthe arrangement position for the position detection mark M_(k) isdistant from the notch N in −β direction from a point of view for thedetection accuracy.

In parallel with the above-mentioned detection, according to the changeof the border position in the observation field, the main controller 20decides whether the border between the chip area CA (i, j₀+1) and thestreet line Sβ_(j0) can be continuously caught or not in the observationfield in the moving direction of the wafer W at the time. When the maincontroller 20 decides that the border might be continuously caught inthe observation field, the wafer W is subsequently continued to be movedas it is. On the contrary, the controller decides that the border cannot be continuously caught in the observation field, according to theapproximation arrangement coordinate system already corrected, thecontroller 20 amends the moving direction of the wafer W, or make themoving direction of the wafer W coincide with the corrected β′-axisdirection.

Thus, the observation field gradually closes to the street line sa idlywhen it traces the street line Sβ_(j0), catching the border between thechip area CA(i, j₀+1) and the street line Sβ_(j0). When the maincontroller 20 recognizes this situation by using the positionalinformation through the wafer interferometer 28, the controller 20decreases the moving velocity of the wafer W for low speed movement.Subsequently, the cross point of the street line Sβ_(j0) and the streetline Sα_(i−1) is searched. The main controller 20 terminates themovement of the wafer W for which the observation field can trace thestreet line Sβ_(j0), when the crossing image formed by the street lineSβ_(j0) and Sα_(i−1), for example, shown in FIG. 7C, is caught in theobservation field.

Then, the main controller 20 decides the positional relation between thestreet line Sβ_(j0) and the position detection mark M₁ from the chiparea information CID₁ of the mark information MP₁. The controller 20recognizes the direction of the street line Sα_(i−1) to be traced by theobservation field. Then the wafer W is moved so that the observationfield traces the border between the street line Sα_(i−1) and the chiparea CA (i, j) to the recognized direction. During this movement as thesame that the observation field traces the street line Sβ_(j0), thechange of the border position is detected. Then, the approximationarrangement coordinate system already corrected is continuouslycorrected according to the detection result. Alternatively, according tothe detection results, the moving direction of the wafer W is amended orrotated if necessary, so that the border between the street lineSα_(i−1) and the chip area CA (i, j) is continuously caught by theobservation field. When the observation field reaches the crossing pointformed by the position detection mark M₁ and the nearest street line tothe mark, i.e., that point is formed by the street lines Sα_(i−1) andSβ_(j−1), the main controller 20 terminates the movement of the wafer Wwhich is used for the observation field to trace the street lineSα_(i−1).

Return to FIG. 4, in step 215, the wafer W is moved so that the positiondetection mark M₁ is caught by the observation field based on theapproximation arrangement coordinate system already corrected withconsidering the identification information MID₁ of the mark informationMP₁ together with the known distance XL0. Then, in step 217, theposition of the position detection mark M, in the reference coordinatesystem (X, Y) is detected from the observation image obtained by thealignment detection system AS to be memorized in the main controller 20.

In step 219, it is decided whether the position detection for all of theposition detection mark M_(k) is conducted or not, i.e., k=p or not. Inthis step, the position detection for the position detection mark M₁ isonly conducted, and then goes to next step 221. In step 221, theparameter k is incremented (k k+1). The parameter k is set to 2 torepresent to visit the second position detection mark M₂ hereinafter.

In step 223, considering the condition of the approximation arrangementcoordinate system corrected by using the detection for the change of theborder position and its detection results up to that time, the maincontroller 20 decides whether the corrected approximation arrangementcoordinate system corrected by the detection of the street line iscorresponded to the true arrangement coordinate system (α, β) withenough accuracy. When it is decided that the approximation arrangementcoordinate system has enough accuracy, the corrected approximatecoordinate system is set as the second approximation coordinate (α″,β″). After that, in the visiting by the observation field to theposition detection mark M₂, the observation field moves the minimumdistance up to the position of the position detection mark M_(k) whichis obtained according to the second approximation coordinate (α″, β″).On the contrary, when it is decided that the corrected approximationarrangement coordinate system does not have enough accuracy, steps 213to 221 are conducted as the same manner that the position detection markM₁ is visited as mentioned above. That is, according to the orderinformation SQ₂, the wafer W is moved so that the observation fieldtakes the route, that is, the street line formed on the wafer. Then, theapproximation arrangement coordinate system in corrected.

After that, in step 219, similarly to the above, the position detectionof the position detection M_(k) is conducted until it is decided thatthe all of the position detection mark M_(k) are detected. When it isdecided that the position detection for the all of the positiondetection mark M_(k) is conducted in step 219, the main controller 20performs statistical procedure in step 225, based on the memorizeddetection result of the position detection mark M_(k). The statisticalprocedure is carried out by using the techniques disclosed, for example,Japan laid-open No. S61-44429 and its corresponding U.S. Pat. No.4,780,617, Japan laid-open No. H02-54103 and its corresponding U.S. Pat.No. 4,962,318, and so forth. By using statistical processing, thepositional relation between the reference coordinate system (X, Y) andthe arrangement coordinate system (α, β) is detected with high accuracyto be conducted fine alignment. The disclosure described in the above isfully incorporated by reference herein, as far as the law of thecountries designated in a request or elected in a demand for theapplication filed in the country of origin permits them.

The second layer is exposed as the same manner that for that of thefirst layer, according to the thus detected the positional relation withhigh accuracy between the reference coordinate system (X, Y) and thearrangement coordinate system (α, β). For exposure to the third andsubsequent layers, they are exposed as the same manner that for thesecond layer. That is, the positional relation between the referencecoordinate system (X, Y) and the arrangement coordinate system (α, β) isdetected with high accuracy, and the position of chip area CA (i, j) isdetected with high accuracy.

Therefore, in the above-mentioned embodiment, the position detectionequals to the conventional search alignment, is conducted during theperiod that is not conventionally used for the measurement. In thisperiod, the wafer W and the observation field of the alignment detectionsystem are relatively moved to conduct the multi-layer exposure withgood overlay accuracy. As a result, the search alignment step which wasconventionally performed and essentially needed may be skipped.Therefore, the positional relation between the reference coordinatesystem (X, Y) and the arrangement coordinate system (α, β) might bedetected in high speed, maintaining high accuracy. Thereby reducing theexposure step, i.e., exposure through put is enhanced. Furthermore,since the alignment detection system AS does not need two observationsystems; one is the low magnifying power observation field for thesearch alignment, and the other is the high magnifying power one forfine alignment, the composition of the alignment detection system ASbecomes simply.

Further, in the exposure apparatus 100 of the present embodiment,elements shown in FIG. 1 such as the above-mentioned illumination system10, the rough alignment system RAS, the alignment system AS, andprojection optical system PL are connected electrically, mechanicallyand optically to assemble the apparatus 100. After that, the apparatus100 is totally adjusted (electrical adjustment or inspection of theoperation) to produce the exposure apparatus 100. The production of theexposure apparatus 100 is preferably produced in a clean room in whichtemperature and cleanliness of the air are controlled.

An embodiment of a device manufacturing method by using the exposureapparatus and method above will be described.

FIG. 8 is a flow chart showing an example of manufacturing a device (asemiconductor chip such as an IC, or LSI, a liquid crystal panel, a CCD,a thin film magnetic head, a micromachine, or the like). As shown inFIG. 8, in step 301 (design step), function/performance is designed fora device (e.g., circuit design for a semi conductor device) and apattern to implement the function is designed. In step 302 (maskmanufacturing step), a mask on which the designed circuit pattern isformed is manufactured. In step 303 (wafer manufacturing step), a waferW is manufacturing by using a silicon material or the like.

In step 304 (wafer processing step), an actual circuit and the like areformed on the wafer W by lithography or the like using the mask andwafer prepared in steps 301 to 303, as will be described later. In step305 (device assembly step), a device is assembled by using the waferprocessed in step 304. Step 305 includes process such as dicing, bondingand packaging (chip encapsulation).

Finally, in step 306 (inspection step), a test on the operation of thedevice, durability test, and the like are performed. After these steps,the device is completed and shipped out.

FIG. 9 is a flow chart showing a detailed example of step 304 describedabove in manufacturing the semiconductor device. Referring to FIG. 9, instep 311 (oxidation step), the surface of the wafer is oxidized. In step312 (CVD step), an insulating film is formed on the wafer surface. Instep 313 (electrode formation step), an electrode is formed on the waferby vapor deposition. In step 314 (ion implantation step), ions areimplanted into the wafer. Steps 311 to 314 described above constitute apre-process for the respective steps in the wafer process and areselectively executed in accordance with the processing required in therespective steps.

When the above pre-process is completed in the respective steps in thewafer process, a post-process is executed as follows. In thispost-process, first, in step 315 (resist formation step), the wafer iscoated with a photosensitive agent. Next, as in step 316, the circuitpattern on the mask is transcribed onto the wafer by the above exposureapparatus and method. Then, in step 317 (developing step), the exposedwafer is developed. In step 318 (etching step), and exposed member on aportion other than a portion where the resist is left is removed byetching. Finally, in step 319 (resist removing step), the unnecessaryresist after the etching is removed.

By repeatedly performing these pre-process and post-process, multiplecircuit patterns are formed on the wafer.

In the above-mentioned embodiment, prior to fine alignment, roughalignment is conducted. However, when pre-alignment is conducted beforethe wafer W is loaded on the substrate table 18 and its accuracy isenough for the observation field to trace the border between the streetline and the chip area, rough alignment step (step 203) may be skippedin the present embodiment; thereby rough alignment detection system RASbecoming unnecessary.

In the above-mentioned embodiment, two position detection marks areformed on each chip area, and chosen marks among them are used forposition detection to perform EGA. However, the present invention mayapply on so-called multiple point EGA in a shot, in which four positiondetection marks are formed on each chip area, and chosen marks amongthem are used for the actual position detection, disclosed in Japanlaid-open No. H06-275496 and its corresponding U.S. patent applicationNo. 183,879 (filing date: Jan. 21, 1994) and its CIP application No.569,400 (filing date: Dec. 8, 1995). The disclosure described in theabove is fully incorporated by reference herein, as far as the law ofthe countries designated in a request or elected in a demand for theapplication filed in the country of origin permits them.

Further, in the above-mentioned embodiment, it is explained the case inwhich the dioptric system is used as the projection optical system PL.However, catoptric system or cato-dioptric system may be used as theprojection optical system. The projection optical system may be reducingsystem or magnifying system.

The present invention may apply on any type of the wafer exposureapparatus, for example, the reduced projection exposure apparatus ofwhich light source is ultraviolet and soft X-ray with its wave lengthabout 10 nm, X-ray exposure apparatus of which light source is X-raywith its wave length 1 nm, EB (electron beam) or ion beam exposureapparatus. Furthermore, the present invention may apply on bothstep-and-repeat machine and step-and-scan machine.

Also, the present invention may apply on step-and-stitching machine. Inthis machine, a plurality of the divided circuit patterns is patched onthe substrate to transfer one large circuit pattern on it. When thedivided circuit patterns are patched on the substrate, respectivepattern is transferred to the substrate overlapping each overlappingarea having predetermined width. Step-and-stitching machine includes themachine in which the divided patterns are transferred by step-and-repeatmanner or by step-and-scan manner.

INDUSTRIAL APPLICABILITY

As described above, according to the position detecting method and theposition detecting apparatus of the present invention, the equalposition detection to the search alignment may be conducted during theperiod which is necessary for fine alignment and is not conventionallyused, and in the period relative movement of the substrate and theobservation field. Therefore, the conventional search alignment step maybe skipped. Accordingly, the position detecting method and the positiondetecting apparatus of the present invention are preferable for theposition detection of the divided areas which are formed on thesubstrate and divided by the street lines in high speed and in highaccuracy.

Further, according to the exposure method and the exposure apparatus,the divided areas formed on the substrate are detected by the positiondetecting method of the present invention, and then high speed andhighly precise position detection is conducted. After that, the dividedareas are exposed, and the pattern formed on the mask is transferredonto the substrate. Accordingly, the exposure method and the exposureapparatus of the present invention are preferable to perform multilayerexposure, which is conducted to form multilayer patterns, holding theoverlay accuracy between layers with enhanced through put. Accordingly,the exposure apparatus is preferable for mass-production of the deviceshaving fine patterns.

1. A position detecting method for detecting positions of a plurality ofdivided areas divided by street lines on the substrate, by using anobservation optical system, said position detecting method comprising:performing image pickup of a boundary between at least one said streetlines and at least one of said divided areas on said substrate, whilerelatively moving said substrate and an observation field of saidobservation optical system in a direction perpendicular to an opticalaxis direction of the observation optical system; detecting a positionalchange of said boundary in a different direction from a direction ofsaid relative movement, based on image information obtained in saidimage pickup during the relative movement; and detecting a positionalrelation between a reference coordinate system that defines a movementof said substrate, and an arrangement coordinate system that correspondsto an arrangement of said plurality of divided areas on the substrate,based on the detected positional change of said boundary.
 2. Theposition detecting method according to claim 1, wherein in saidperforming image pickup, said image pickup of said boundary is performedat regular intervals during said relative movement.
 3. The positiondetecting method according to claim 1, wherein said positional change ofsaid boundary is detected in a direction substantially perpendicular toa direction of said relative movement in a two-dimensional planeincluding the direction of the relative movement.
 4. The positiondetecting method according to claim 3, wherein the detection of saidpositional change of said boundary is performed during said relativemovement.
 5. The position detecting method according to claim 3, whereinsaid positional relation is detected, based on a positional change ofsaid at least one of said street lines in a direction perpendicular tothe direction of said relative movement while the relative movement isperformed.
 6. The position detecting method according to claim 5,wherein prior to the detection of said at least one of said streetlines, an outer edge of said substrate is measured, and based on themeasurement result, said positional relation between said referencecoordinate system and said arrangement coordinate system is detectedwith predetermined accuracy lower than accuracy with which thepositional relation is detected while the relative movement isperformed.
 7. The position detecting method according to claim 6,wherein said substrate is rotated so that an axis direction of saidreference coordinate system is parallel to an axis direction of saidarrangement coordinate system, based on said positional relationdetected with said predetermined accuracy.
 8. The position detectingmethod according to claim 5, wherein said observation field isrelatively moved with respect to said substrate along said at least oneof said street lines.
 9. The position detecting method according toclaim 8, wherein in the detection of said at least one of said streetlines, a positional change of a border between said at least one of saiddivided areas and said at least one of said street lines within saidobservation field is measured by observing a moving picture within saidobservation field while relatively moving said substrate and theobservation field, and said positional relation is detected based on themeasurement result of the positional change of said border.
 10. Theposition detecting method according to claim 9, wherein when it ispresumed that said border is out of range of said observation field, therelative movement of said substrate and said observation field iscorrected so that the border is continuously caught within theobservation field.
 11. The position detecting method according to claim9, wherein in the detection of said at least one of said street lines,an image formed by a total quantity of light that reaches each pointwithin said observation field is picked up during a predetermined pickuptime, and said positional change of said border within the observationfield is measured based on the pickup result.
 12. The position detectingmethod according to claim 1, wherein said positional change of saidboundary is detected by obtaining image information through picking upan image of said boundary.
 13. The position detecting method accordingto claim 1, wherein said relative movement of said substrate and saidobservation field is performed so that a predetermined number ofposition detection marks, which are chosen from a plurality of positiondetection marks formed on said at least one of said street lines, arecaught within the observation field in predetermined order, a positionof the chosen predetermined number of position detection mark isdetected, and based on the detection result, said positional relation isdetected with higher accuracy than accuracy with which the positionalrelation is detected while the relative movement is performed.
 14. Aposition detecting apparatus that detects positions of a plurality ofdivided areas divided by street lines on a substrate, said positiondetecting apparatus comprising: a substrate stage that holds saidsubstrate; an observation system that performs image pickup of saidsubstrate by using an observation optical system; a driving unit thatdrives said substrate stage in a direction perpendicular to an opticalaxis direction of said observation optical system; and a processing unitthat is electrically connected to the observation system, and obtains apositional relation between a reference coordinate system that defines amovement of the substrate stage, and an arrangement coordinate systemthat corresponds to an arrangement of said plurality of divided areas onthe substrate, based on image information regarding a boundary betweenat least one of said street lines and at least one of said divided areasobtained by the observation system while the substrate stage is moved bysaid driving unit.
 15. The position detecting apparatus according toclaim 14, wherein said observation system observes a positional changeof said boundary in a direction substantially perpendicular to a movingdirection of said substrate stage during the movement of said substratestage.
 16. The position detecting apparatus according to claim 15,further comprising: a control system that is electrically connected tosaid driving unit, and controls the driving unit so that said at leastone of said street lines is detected by said observation system whilemoving said substrate stage, when detecting a mark on said substrate.17. The position detecting apparatus according to claim 16, wherein saidcontrol system controls said driving unit so that said observation fieldof said observation system follows a route to a predetermined positiondetection mark that is chosen from the position detection marks formedon said at least one of said street lines, and the control systemfurther detects a position of the chosen predetermined positiondetection mark and detects a position of each divided area based on thedetection result of the chosen predetermined position detection mark.18. The position detecting apparatus according to claim 17, wherein saidroute is along a street line.
 19. The position detecting apparatusaccording to claim 14, wherein said observation system comprises animage pickup apparatus that obtains image information by performingimage pickup of a substrate surface.
 20. An exposure method in which apredetermined pattern is transferred to a divided area on a substrate byemitting an energy beam, said exposure method comprising: detecting aposition of said divided area formed on said substrate by using theposition detecting method according to claim 1, prior to said transfer.21. An exposure apparatus that transfers a predetermined pattern to adivided area on a substrate by emitting an energy beam, said exposureapparatus comprising: an illumination system that emits said energybeam; and the position detecting apparatus according to claim 14 thatdetects a position of said at least one of said divided areas.
 22. Amaking method of a position detecting apparatus that detects a pluralityof divided areas divided by street lines on a substrate, said methodcomprising: providing a substrate stage that holds said substrate;providing an observation system that performs image pickup of saidsubstrate by using an observation optical system; providing a drivingunit that drives said substrate stage in a direction perpendicular to anoptical axis direction of said observation optical system; and providinga processing unit that is electrically connected to the observationsystem, and obtains a positional relation between a reference coordinatesystem that defines a movement of the substrate stage, and anarrangement coordinate system that corresponds to an arrangement of saidplurality of divided areas on the substrate, based on image informationregarding a boundary between at least one of said street lines and atleast one of said divided areas obtained by said observation systemwhile the substrate stage is moved by said driving unit.
 23. A devicemanufacturing method comprising a lithographic process, wherein apredetermined pattern is transferred onto a divided area divided bystreet lines on said substrate, by using the exposure method accordingto claim
 20. 24. A device manufactured by using the device manufacturingmethod according to claim
 23. 25. The position detecting methodaccording to claim 1, wherein: based on said detected positionalrelation between said reference coordinate system and said arrangementcoordinate system, a direction of the relative movement is changed whilerelatively moving said substrate and said observation field.